It’s hard to believe, but after two series of emotional anguish, Lady Mary Crawley actually has a smile on her face.

“The big difference for Lady Mary in this series is that she’s very happy!” enthuses Michelle Dockery. “As much as that angst between Matthew and Mary was enjoyable to play, I must say it’s lovely now to be settled in some ways.”

But first we have the prospect of the nuptials – and one of the most eagerly anticipated wedding dresses of the last few years.

“It’s an absolutely stunning design,” says Dockery. “Caroline McCall [costume designer on series three] did such an extraordinary job. She’s really talented. She worked with Susannah Buxton [costume designer on series 1 and 2] – the master! – for two years so inevitably she’s just as brilliant.

“It’s a truly stunning dress. I’m sure that people will make some comparisons with the royal wedding. The crowds as we arrived at the church and stepped out of the carriage were just amazing, with all these supporting artists cheering us on.”

Of course, whether Lady Mary and Matthew actually tie the knot is up for debate, but has this impending union made Lady Mary easier to like? She did have quite the reputation for frostiness during the show’s earliest episodes…

“In the first few episodes people loved to hate her. She was very cold, she had this icy exterior and she was vile to her sister. Then, half-way through the first series, after the incident with Pamuk [the Turkish diplomat who died in Lady Mary’s bed], she began to soften.

“Then in the second series you see the heart of the character much more because, of course, we were at war – every time she saw Matthew could have been the last. And I’ve loved that arc that Julian [Fellowes] has written for her. Even in the third series it’s changing.”

Dan Stevens (Matthew Crawley)

They’re the questions that are preoccupying all Downton fans: what is the wedding between Matthew and Lady Mary going to be like? And can we expect something on the scale of Prince William and Kate Middleton?

“I don’t know if they’ll quite get that!” says Dan Stevens. “The kiss on the balcony? I don’t think so. It will look very beautiful. Michelle [Dockery] looked fantastic in the dress.”

Yet despite all this talk of impending nuptials (and who’s to say whether the wedding will go ahead?), Stevens is most excited by a series-three plot point that has nothing to do with marriage. It was getting to play cricket – in 1920s fashion. A keen cricketer himself, Stevens was all-too-keen to get dressed up in flannels and play a match on Highclere Castle’s own cricket pitch:

“It was perfection. I was all padded up, out in the middle, had an entire team of extras bowling at me and fielding. And when I got out, I was able to stay in so we could do another take.”

So is Matthew Crawley now feeling more at home on the estate? Or are there further ructions to come?

“It’s a question of whether they’re going to stick around or not. Matthew’s a bit iffy about staying in the house. I think he wants a certain amount of independence before taking on Downton. So I think it’s his idea that maybe they’ll go and live elsewhere. And then, as the series progresses, he gets a bit more involved with the estate and sees a few weak spots in the management.”

And will this cause fireworks for the family and with Lady Mary?

“There’s a slight lack of sensitivity on Matthew’s part that I think occasionally shows its face…well, let’s just say he doesn’t always pick his moments in the best way. So yes, that’s a big part of what he’s up to this year.

“His relationship with Mary has changed. They’ve both matured a little. I think it’s that growing sense of responsibility becoming more of a reality. The older they get, the further on it goes and the more involved he gets in the estate.”

Jessica Brown Findlay (Lady Sybil Crawley)

When we meet the youngest Crawley sister again, she’s largely shaken herself free of her role as an aristocrat and has settled herself in to her life as ‘Mrs Branson’. Then there’s the fact that Lady Sybil is expecting her first child – something that, thanks to a prosthetic pregnant belly, was a lot of fun for actress Jessica Brown Findlay:

“Endless amusement,” the actress admits. “Once I had my pregnant belly on and Allen [Leech who plays Sybil’s husband Branson] kept telling everyone that I hadn’t got it on – so they’d just think I was fat.”

And how has Lady Sybil changed in her time away from Downton?

“A lot has changed for Sybil but we find her incredibly happy and settled. She’s been able to find her identity. She’s spent these months in Ireland with Branson, she’s had the joy of work, she’s felt an independence and she’s completely accepted there. She’s just really content.”

But, of course, all that is set to change thanks to the “Irish question” looming large over life at Downton – a turn of events that leaves Sybil and Branson feeling exposed:

“A big concern is the Irish Problem: her involvement in that and what it will mean in terms of the freedoms they will or will not have to come back and forth to the house. She’s in quite a tricky position. She needs to come back because her family demands it but she also needs to not take too much of an English stance on Ireland.